Power factor responsive control systems for alternating current motors have been known heretofore. For example, F. J. Nola U.S. Pat. No. 4,052,648, dated Oct. 4, 1977, shows a single-phase power factor control system for an A.C. induction motor that samples line voltage and current through the motor and decreases power input to the motor proportional to the detected phase displacement between current and voltage to thereby provide less power to the motor as it is less loaded. For a three-phase motor, three of the control systems illustrated in this patent would be used, one being connected in each of the three phases with each referenced to ground in the case of a wye-connected motor. In a delta-connected motor, a triac and sampling resistor is placed in series with each winding of the motor and the voltage is taken across the two power leads for the respective winding.
Also, C. L. Wanlass U.S. Pat. No. 4,152,630, dated May 1, 1979, shows an A.C. induction motor that uses capacitors and a control winding on the stator to cause the motor to consume considerably less electrical energy than conventional motors.
While these prior systems have been useful for their intended purposes, this invention relates to improvements thereover.